问NoMethodError on控制器方法Rails 5

EN

Started PUT "/course_modules/module-1-understanding-email-marketing-basics/complete" for 127.0.0.1 at 2018-09-19 16:29:42 +0100
Processing by CourseModulesUsersController#complete as HTML
  Parameters: {"authenticity_token"=>"CfIM56PhiIRumytV99CE7GFK6tYumCgDvBwUS79jhbCr3zpXLfbJgvqUFkzwmKLXQiOxk1SmFvGoO4+M1z87wg==", "id"=>"module-1-understanding-email-marketing-basics"}
  CourseModulesUser Load (0.7ms)  SELECT  "course_modules_users".* FROM "course_modules_users" WHERE "course_modules_users"."id" = $1 LIMIT $2  [["id", 0], ["LIMIT", 1]]
  ↳ app/controllers/course_modules_users_controller.rb:3
Completed 500 Internal Server Error in 6ms (ActiveRecord: 0.7ms)



NoMethodError (undefined method `complete=' for nil:NilClass):

app/controllers/course_modules_users_controller.rb:4:in `complete'

irb(main):017:0> @course_modules_users = CourseModulesUser.find_by(id: 1)
  CourseModulesUser Load (0.4ms)  SELECT  "course_modules_users".* FROM "course_modules_users" WHERE "course_modules_users"."id" = $1 LIMIT $2  [["id", 1], ["LIMIT", 1]]
=> #<CourseModulesUser id: 1, course_module_id: 1, courses_user_id: 1, complete: false, created_at: "2018-09-19 13:04:16", updated_at: "2018-09-19 14:58:17">
irb(main):018:0> @course_modules_users.complete = true
=> true

<% if @course_modules_users.where(complete: true).nil? %>
  <i class="fas fa-check text-green float-left mr-1"></i>
  <span class="text-xs mr-2">Completed</span>
<% else %>
  <%= link_to complete_course_module_path(course_module), method: :put do %>
  <i class="fas fa-check text-grey-darkest float-left mr-2"></i>
  <% end %>
<% end %>